Method of making lead alloys



Patented Oct. 20, 1936 METHOD OF MAKING LEAD ALLOYS Sidney M. Hull, Western Springs, 111., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York No Drawing. Application December 8, 1933,

Serial No. 701,539

10 Claims. (01. 75-167) This invention relates to methods of making lead alloys and more particularly to methods of making alkaline earth metal alloys of lead.

It has been known for some time that the alloying of certain metals with lead, such, for example,

' as calcium, increases the hardness of the lead,

making it suitable for many purposes for which pure lead is undesirably soft.

An object of the present invention is to provide an economical and effective method of making lead alloys. 7

In accordance with one embodiment of the invention, calcium carbide and aluminum are heated in a molten bath of lead, causing the aluminum to combine with the carbon of the calcium carbide to release metallic calcium to the lead.

In the manufacture of age-hardened lead-calcium alloys, as described in the patent to R. S. Dean No. 1,890,013, December 6, 1932, it is enstomary to use a lead-calcium alloy having from .02% to .1% of calcium. This small quantity of calcium in the alloy makes it desirable to first make an intermediate alloy having a considerably higher percentage of calcium and then mixing the intermediate allow with substantially pure lead.

The intermediate alloy may be made in accordance withthe present invention by heating lead inthe presence of calcium carbide and aluminum. The reaction between the calcium carbide and aluminum is believed to be as follows:

4CaC2+6Al=2Al3C4+4Ca, and the reaction is exothermic since the aluminum carbide has a gram molecular heat of formation of 232,000 calories on the basis of an ambient temperature of 15 C. This exothermic reaction indicates'a high degree of stability of the aluminum carbide, and the equilibrium between the calcium carbide and aluminum'carbide is at such a point as to allow a large portion of metallic calcium to be liberated to be alloyed with the lead.

In' practicing the invention i884 parts of lead may be placed in a graphite crucible and 40 parts of granular aluminum and parts of calcium carbide added. The mixture is then heated for one hour at a temperature from 2500 to 3000 F. in an induction furnace. Lower temperatures may be used although the yield of calciumin the lead will be lower. The graphite crucible is covered with a graphite lid loosely placed thereover and the graphite crucible at this temperature provides a carbonaceous reducingatmosphere over the bath during the treatment. The inducalloy-made by this method upon analysis proved A small to have a calcium content of 1.69%. portion of aluminum appears to enter the leadcalcium alloy thus made. As far as is known aluminum is not miscible with lead either in the solid or molten state and may, therefore, be removed by allowing it to remain unagitated in the molten state to provide an opportunity for the aluminum to rise to the top. However, in many cases it is desirable to allow a small percentage of aluminum to remain in the lead-calcium alloy due to the fact that when the intermediate alloy is mixed'with lead, as pointed out above, the presence of aluminum prevents oxidation and loss of calcium during the mixing with the lead.

In manufacturing calcium lead alloys on a large scale, it is desirable to use a rocking arc furnace provided with a suitable lining. The are itself provides a reducing atmosphere and this is supplemented by covering the bath with a carbonaceous material, such as lamp black or coke, to prevent oxidation.

In order to promote the reaction between the calcium carbide and the aluminum, these materials may be finely subdivided or powdered. Care must be taken in pulverizing the calcium carbide to carry out this operation in a dry atmosphere to prevent moisture of the air from combining with the calcium carbide to form acetylene.

It will be understood that the nature and embodiments of the invention herein described are merely illustrative and many changes and modifications may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A method of makingan alloy of lead and an alkaline earth metal, which comprises adding a carbide of said metal together with aluminum to the lead, and heating the materials to cause the aluminum to react with the carbide and release the alkaline earth metal to the lead.

2. A method of making lead-calcium 'alloys which comprises heating a lead bath in the presence of calcium carbide and aluminum to precipitate metallic calcium and alloy it with the lead.

3. A method of making lead-calcium alloys which comprises heating calcium carbide and an aluminum in a lead bath in a carbonaceous atmosphere.

4. A method of making lead-calcium alloys which comprises heating calcium carbide and aluminum in a. lead bath under a covering of a carbonaceous material. a

5. A method of making lead-calcium alloys which comprises heating calcium carbide and aluminum in a lead bath by means of a reducing arc.

6. A method of making lead-calcium alloys which comprises heating finely divided calcium carbide and finely divided aluminum over a lead bath to precipitate metallic calcium into the lead.

8.'A method of making alloys of lead and alkaline earth metals, which comprises adding aluminum and a carbide of an alkaline earth metal to molten lead, and causing the aluminum to react with the carbide to release the alkalineearth metal and form an alloy of the latter with the lead.

cium, which comprises adding calcium carbide and aluminum to molten lead, and causing the aluminum to replace the calcium in the carbide and thereby release the calcium to form an alloy with the lead.

10. A method of making alloys of lead and alkaline earth metals which comprises heating an alkali earth metal carbide in a lead bath to free the alkali earth metal from the carbon of said compound, combining the nascent carbon with a metal having an exothermic reaction with carbon to augment the heat applied to further the disas'sociation of the carbide and release the alkaline earth metal to the lead bath.

. SIDNEY M. HULL.

9. A method of making alloys of lead and cal- 

